A magnetically shielded room, commonly referred to as an "MSR," is used to magnetically and electromagnetically isolate sensitive instruments and equipment such as highly sensitive biomagnetic detectors, measuring instruments, and super conductive quantum interference devices, commonly referred to as "SQUIDs." The sensitive instruments are used among other things for biomagnetic research and tests to measure minute magnetic fields. To obtain proper readings and results from the sensitive equipment, the environment for conducting these tests must be extremely magnetically quiet. The MSR provides a magnetically and electromagnetically isolated environment for using this equipment by attenuating stray magnetic fields and other magnetic disturbances created or generated by the earth's magnetic field, power lines, current carrying conductors and moving metal masses such as trains, automobiles, elevators and other large metal objects in the vicinity of the MSR. Except for the power lines which create 50/60 hertz frequencies, the above mentioned influences create low or very low frequencies which often approach DC or zero. The earth's magnetic field is in fact a DC field. Since magnetic and electromagnetic shielding of DC and low frequencies is difficult to obtain, the ideal MSR includes multiple shells which have shielding layers or shields of very high magnetic permeability and highly electrically conductive materials capable of attenuating these various frequencies.
The MSR must also provide a stable and homogeneous environment for the small, if any, remaining residual field in the MSR near the measuring instrument. To achieve this stable and homogeneous environment, the MSR is preferably a six sided cube having a floor, a ceiling, four walls and a door in one of the walls for providing access to the interior chamber of the MSR. In the ideal MSR, the floor, ceiling, walls and door have multiple magnetic and electromagnetic shielding layers or shields to obtain high attenuation characteristics and to produce the desired stable and homogeneous environment in the interior chamber of the MSR. To obtain this stable and homogenous environment, the shielding layers or shields must be continuous or provide substantial continuity of the electric and magnetic flux in the electrically conductive and magnetically permeable shielding layers or shields. It is difficult to achieve this continuity between the door of the MSR and the surrounding walls or door frame due to the physical separation necessary to form the door.
To achieve the continuity between the door and the door frame, all air gaps must be eliminated between the outer peripheral edge of the multiple shielding layers or shields in the door and the inner edge of the door frame. Ideally, a substantial, continuous and even pressure is required between the door and the door frame. Previous MSRs have employed a single door having multiple layers. However, due to manufacturing tolerances and the size of the air gap between the multiple layers or shields, a one piece door will not guarantee the desired uniform electric and magnetic continuity between the door and the door frame or between the doors and the shielding layers or shields adjacent to the door. Moreover, conventional door hinges and conventional locking mechanisms will not provide the desired continuous contact to eliminate the air gaps between the shielding layers or shields in the door and door frame.